In wireless communication systems, a set of packet formats is used at the access network (AN) and the access terminal (AT) to facilitate communication between the AN and the AT. A packet format defines the packet size, modulation, and effective coding rate of the transmitted packet. For AN based packets, the AN transmits an indication of the packet format to the AT using a control channel and transmits the associated packet using the data channel. This indication is received at the AT and, based on the associated packet format, the AT is able to correctly process the packet received on the data channel. The control channel may also contain additional control information such as the amount of system resources used to transmit the packet.
It is generally desirable to reduce overhead associated with indicating the packet format. To accomplish this, the set of packet formats is typically limited to a small number. For example, if there are 16 packet formats, the AN can indicate the selected packet format to the AT with 4 bits. Similarly, the AT can indicate the packet format it would like the AN to use, in the form of a channel quality indication, with 4 bits.
Limiting the set of packet formats results in quantization of the transmission properties of the packet. In particular, there are only as many combinations of packet size, modulation, and effective coding rate as can be derived from the set of packet formats.
Certain applications such as voice over internet protocol (VoIP), video telephony (VT), and gaming can have a particular packet size. If the packet size does not match one of those that can be derived from the set of packet formats, the AN must pad the packet, for example with zeros, before transmitting the packet to the AT. This results in additional overhead, thereby reducing system capacity.
The various aspects, features and advantages of the present disclosure will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description thereof with the accompanying drawings described below. The drawings may have been simplified for clarity and are not necessarily drawn to scale.